Digital products, e.g., computer software and data, have been published widely through a variety of methods and mediums. Publishers have sold and distributed digital products like other products, e.g., packaged and available at retail outlets or through catalog and mail-order delivery. The nature of digital products, however, lends itself to non-traditional methods of distribution. Because common devices, e.g., personal computers and modems, duplicate digital material without degradation, consumers can copy and distribute reliably most digital products. Examples include shareware and distribution by modem via computer bulletin boards or the well-known Internet global communication medium. A second popular digital product distribution mechanism is CD-ROM, a relatively inexpensive medium having vast storage capacity, allowing publishers to distribute on a single disk a large volume of digital material including supporting documentation and manuals.
Such methods of broad distribution attract both publishers and end-users of digital products. Widespread distribution of fully functional digital products occurs accurately and without significant cost to the publisher. End-users access a variety of products for comparison with opportunity to actually try each product before making a decision to purchase. In essence, the end-user receives the fully functional digital product as an offer to purchase based on an opportunity to fully evaluate the actual product. The publisher profits when the evaluation process yields sufficient purchasers. This "try-before-you-buy" distribution mechanism is especially attractive in the context of global communication networks such the Internet where distribution occurs globally at minimal cost and where an enormous number of potential purchasers of digital products interact.
Unfortunately, the ability to accurately copy and make use of digital products lends itself to unauthorized use of digital products by unauthorized users. For example, persons using the digital product fully and indefinitely beyond an initial evaluation period take value from the publisher. Digital products may be easily reproduced and the publisher can take advantage of this characteristic as a distribution mechanism, however, the publisher risks unauthorized use and lost sales under such a distribution mechanism without some form of control over product execution. The digital product publisher taking advantage of such broad distribution schemes must implement some form of control to prevent unauthorized use of the digital product while still making the product widely available for consumer-evaluation.
Early attempts to control use of published digital products included distribution of an "evaluation" copy of a digital product. The evaluation copy, "diminished" relative to the actual product, introduced the consumer to the product, but wouldn't allow or even include code supporting fully functional use. To produce the evaluation copy, the product author, e.g., programmer, would rewrite the product in an alternate, i.e., less functional, form. In such product re-design process, difficult issues arose with respect to the degree of inoperability established relative to the fully operational form of the product. Furthermore, a consumer wishing to purchase the product following trial use of the evaluation copy had to obtain a fully functional version through traditional, e.g., retail, distribution mechanisms.
A second, but only slightly more successful, approach contemplated distribution of a "crippled" form of the fully functional product. Distribution material would include a fully functional digital product, but also safeguards incorporated into the product to prevent fully functional use until authorization, i.e., purchase, occurred. For example, a word processing program could not, in its crippled form, print a document or save a document to disk. When, following an evaluation period, the user decided to purchase the product, a purchase procedure "de-crippled" the product for fully functional use. For example, the purchaser received a "key", i.e., a predetermined coded value, required to convert the crippled form of the product to a truly fully functional form. The consumer need not physically obtain a new copy of the product at the time of purchase.
Unfortunately, users demand a truly fully functional form of the product during the evaluation period. To meet such user demand, providers of digital content now distribute a fully functional form of the digital product for evaluation, yet control in some manner the use of the product to prevent unauthorized use, i.e., prevent use beyond an allowed trial evaluation.
A "metering" mechanism used in association with a published "try before you buy" digital product places a limitation on a potential purchaser's use of the digital product. A metering mechanism is required for distribution of a fully functional version of a digital product. Otherwise, the potential purchaser has no reason to become an actual purchaser. A metering limitation might include a time period of allowed use followed by a purchase requirement for continued use. Another common metering limitation is a limited number of uses, e.g., limited number of executions, followed by a purchase requirement for continued use. Important to note, during evaluation the potential purchaser has full use of the product.
Unfortunately, converting a fully functional digital product to a metered form for distribution introduces not only a new and significant production step, but also introduces an opportunity to create flaws or "bugs" in the product. This also tends to introduce complexity into the published product not related to operation of the product itself as designed by the software developer, but complexity as related to implementation of a reliable metering function.
As digital products evolve, especially computer program products, overall size and complexity increase. Software developers hesitate to implement quick solutions for known problems, fearing introduction of yet additional problems. A particular condition or "bug" sometimes requires many specific ordered steps to manifest itself. Software developers use sophisticated software testing scripts providing repeatable recursion testing for past or known "bugs" to insure the quality of the latest version of a given program. Developers endeavor to minimize the resource usage of their products and to keep the size of the programs as small as possible. This can be an especially sensitive problem if the proposed growth of a product requires an increase in the number or type of distribution medium, e.g., adding an additional diskette to a software product is considered a costly requirement.
The need to produce a fully functional demonstration version of a product, i.e., a "try before you buy" version of a product, normally introduces a higher order magnitude of difficulty. Creating a "crippled" version of the full-functioning product and/or controlling usage and maintaining version control of both the crippled version and the non-crippled version is a daunting task, not to mention the need to execute elaborate, e.g., recursion, testing of both versions of the product. In essence, the manufacturer must provide two products instead of one, i.e., doubles the product inventory and associated testing and product management.
Most solutions for such problems faced by software developers require extensive involvement of software programmers, quality control labs, version/source control managers and, most importantly, time. Any "automated" solution to metering or to execution control usually requires the original software programmers to reprogram their final product to utilize the "automated" solution. The "automated" solution is usually in the form of additional development software provided by a third party that needs to be integrated with a final product via programming. This type of solution is commonly referred to as an "SDK" (software development kit) approach. An SDK approach to metering, however, introduces complexity and potential for programming errors unrelated to operation of the product itself. Further, and far from trivial, the use of an SDK approach adds time and cost to the development cycle.
Developers of digital products prefer to simply create the digital product without limitation or additional production steps unrelated to use and operation of the fully functional form of the product. In other words, it is difficult enough to produce a fully functional form of the product as designed without the additional complexity of incorporating safeguards against unauthorized use beyond a trial evaluation.
Thus, distribution of digital products according to the "try before you buy" method should not require that the creator of the digital product modify its design to meet a particular distribution scheme. At present, "try before you buy" distribution schemes typically require some modification of the digital product by the original developer to implement distribution in a metered form, i.e., a controllable form allowing distribution and evaluation of a fully functional product but not allowing long term use.
Ideally, digital products are produced without use limitations or safeguards, leaving the creator of the digital product exclusively to the task of implementing the digital product itself. The present invention allows a creator of a digital product to concentrate on the product itself without requiring the creator to incorporate safeguards or limitations against unauthorized use.
Digital product distribution according to the "try before you buy" distribution method is an example of a need to impose execution control over a digital product. Such execution control has nothing to do with the digital product as designed, but represents an auxiliary feature imposed upon the product and unrelated to the product's operation or function as designed. Other forms of execution control, i.e., other forms unrelated to product execution as designed, include encryption and decryption functions applied for security purposes, compression and decompression functions to conserve media storage space, long term metering of usage for billing purposes or license usage enforcement, and interfacing with other programs or systems or controlling agents to enforce ongoing authorization of use. Generally, these auxiliary control features imposed upon a digital product have purposes unrelated to the execution of the digital product as designed, but rather are imposed for other reasons.
Thus, it is desirable to impose execution control over a digital product, but undesirable to require that such execution control be integrated into the design and production of the digital product. The subject matter of the present invention advantageously isolates digital product design from imposition of auxiliary execution control.
One form or mechanism for imposing control over the execution of an application has previously been available through the use of "TSR" (terminate and stay resident) programs. A TSR program loads into a computer and remains available while any other application might be called upon to run. A TSR is normally thought of as a "DOS"-based facility, but it can provide similar services for Windows (TM) based applications as well. A Windows (TM) "device driver" or "VxD" (virtual device driver) can provide similar services only for Windows (TM)-based applications. However, the use of such TSRs or VxDs to provide execution control, e.g., for metering, is impractical because there is no mechanism to enforce the presence of such a control. The control device must accompany the application to be metered. And more importantly, it is mandatory that it be done in such fashion that metering cannot be avoided, i.e., that the application cannot run unless the metering function or control device permits it. Generally, TSRs and VxDs cannot guarantee such execution control.
Thus, there remains need for improvement in the area of execution control over existing applications. Execution control can be designed into an application. The application designer, however, most preferably ignores any such auxiliary control issues and designs the product strictly according to its intended function. Auxiliary control, preferably, is imposed upon the digital product in its final form as produced according to its design without reference to any such auxiliary control in its original design. The subject matter of the present invention provides a mechanism for imposition of execution control over an application without requiring that the application design include such control features. Under the present invention, the application may be first designed and manufactured to final form as intended with execution control imposed subsequently upon the digital product as taken in its final form.